Device and method for sensing and protection of persons and objects

ABSTRACT

An electronic device including a wave transmitter covering a determined spatial sensing field, and a wave receiver for controlling an automatic device; a radiating antenna including a waveguide having lateral faces and slots arranged on one of the lateral faces, wherein the slots radiate in planes substantially perpendicular to a longitudinal direction of the waveguide, and wherein the wave transmitter and the wave receiver are arranged at one end of the waveguide; a matched load arranged at an opposite end of the wave guide; substantially identical reflectors arranged over substantially the whole length of the waveguide, wherein the reflectors extend essentially symmetrically with respect to longitudinal plane of symmetry of the waveguide and making a predetermined angle with one another, and wherein the waveguide and the reflectors are composed of at least one piece.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to electronic devices for sensing and/orprotection of persons or objects in the immediate environment ofautomatic devices, such as automatic doors or potentially dangerousautomatic devices, so as to avoid any motion or movement of the latterwhich may bring about dangerous contact with these persons or objects.

PRIOR ART

Electronic sensors are known which comprise a transmitter fortransmitting waves or radiations, such as UHF waves or infraredradiations, and a receiver for detecting the reflected waves or thescattered radiation reflected by an obstacle situated in the spatialfield covered, so as to produce a sensing signal depending on thecharacteristics of the reflected radiation. In this regard, Dopplereffect UHF motion sensors, which conventionally installed on the upperpart of an automatic door cover a spatial sensing field whose shape anddimensions are determined by the antenna used and which have thefunction of controlling the opening of the door following the sensing ofthe motion of a person or object in the sensing field, are known.

Generally, it is desired that the sensing lobe thus developed by thesensor should be relatively broad and that the sensor should sense anymotion with equal sensitivity, irrespective of the direction of motionof the person or object with respect to the door.

In certain cases it is desirable, however, for the depth of the sensinglobe projected in front of the door to be further reduced. The casepresents itself in particular when the sensor is to control the openingof a door situated in proximity to a sidewalk or in a shopping arcade.It is clearly appreciated, in this case, that the incessant traffic ofpedestrians strolling along the sidewalk or in the arcade, withoutintending to pass through the door, should not cause the untimelyopening of the latter.

The same is true when the sensor is to ensure the protection of personsor objects in the immediate approaches to a revolving door, to apivoting door, or to a slatted or roller shutter door. In this case, thesensor is fixed on the door itself and accompanies it in its motion,whilst monitoring the dangerous environment, that is to say, the spacesituated in front of the moving leaf for a revolving door or a pivotingdoor, or the space surrounding the horizontal leading edge of a rollershutter door. In these cases of application, the depth of the sensinglobe should be reduced so as to avoid, during the motion of the door,and hence of the sensor, sensing persons or objects situated outside thedanger zones.

Solutions known heretofore and based on the use of special hornantennas, enable Doppler effect UHF motion sensors to develop arelatively shallow sensing lobe. A limit exists, however, to thistechnology, which does not make it possible to achieve a depth of lobesubstantially less than a meter.

What was described above applies also to UHF presence sensors, whosefunction, contrary to the sensors mentioned earlier, is to sense thepresence of a person or object stationary in their sensing field, so asto prevent the door performing a dangerous motion. In these applicationcases, the zone to be protected should also be of very reduced depth andsituated in proximity to the door so as to cover only the danger zoneand avoid untimely disabling through the sensing of too far-off apresence.

Other types of sensors, such as active infrared sensors, make itpossible, by virtue of an optic consisting for example of cylindricalFresnel lenses, to sense the presence--and a fortiori the motion--of anybeing or object in a sensing field of very reduced depth constituting asensing or protection curtain.

However, it is well known that optoelectronic presence sensors areparticularly sensitive to the nature, color and reflective power of thebackground which they cover and of the target to be sensed. Depending onthe fixed triggering threshold, the least unforeseen disturbance bringsabout unwanted sensing, and thus the untimely opening or disabling ofthe door, depending on the function of the sensor. The more sensitivethe sensor--this generally being desired so that the coverage which itensures in front of the door extends as near as possible to theground--the more frequent is the occurrence of this spurious sensing.

Solutions exist in order to limit the above-cited drawbacks. However,they involve digital signal processing, thus raising the price of thesensor.

Other types of presence and motion sensors based on measuring thepropagation time of ultrasound waves have, however, some of theabove-cited drawbacks, especially unwanted sensings due to the modifyingof the sensitivity of the sensor as a function of the climaticconditions (temperature, humidity), sensitivity to vibrations, and aircurrents, a common situation in the environment of automatic doors.

Within the framework of the particular application cited above, the maindrawback presented by this kind of sensor originates from the fact thatthe sensing lobe has a virtually circular cross section at ground level.Indeed, the sensing lobe is certainly shallow. By contrast, the widththereof is too small to ensure sufficient coverage.

Moreover, the technology of UHF frequencies or ultrasound, such as usedheretofore, does not enable the sensor to take into account the angularcomponent of the motion of the person or object sensed. Indeed, once theperson or object penetrates into the sensing lobe, the characteristicsof the reflected radiation are modified and the sensor sends a signal tothe automatic unit controlling the door. This occurs whether the movingagent approaches the door perpendicularly intending to enter it, orwhether the agent merely ambles past without intending to enter.

In the case of the sensing of motion in front of a door situated along asidewalk or a zone or area of heavy pedestrian traffic, the attractionof a sensor capable of discriminating the direction of the pedestriantraffic from the mere presence of pedestrian traffic is clearlyappreciated. Indeed, this makes it possible to control the opening ofthe door only to moving agents traveling in a direction, or possessed ofa component of velocity directed, towards the door, and to leave thedoor closed in the event of traffic parallel to the door.

This particular application could find a solution by virtue of infraredsensors having a matrix array of transmitters and receivers. This matrixarray would allow signal processing allied with image processing, fromwhich it would be possible to extract information about the direction aswell as the sense of displacement of the moving agent sensed. Thisprocessing is, however, far from being straightforward, and can but leadto expensive sensors. Moreover, these sensors are subservient to thetechnology used, and they are sensitive to a number of factors such asthe nature, color and reflective power of the background and of thetarget to be sensed.

DISCLOSURE OF THE INVENTION

The purpose of the present invention is to remedy the stated drawbacksand it proposes a device for sensing and protection which makes itpossible to produce a sensing lobe, of reduced depth.

According to the present invention, there is proposed a device forsensing and protection of persons and/or objects in the immediateenvironment of an automatic device, for example an automatic door.

The device comprises a wave transmitter covering a determined spatialsensing field and a reflected-wave receiver controlling the automaticdevice. A radiating antenna consisting of an elongate body has severalradiating slots distributed over the length of the elongate body, eachradiating slot having a shape and a placement which are determined insuch a way that the antenna radiates in planes which are virtuallyperpendicular to the longitudinal direction of the elongate body. Such aradiating antenna ensures with advantage a sensing in a favoreddirection.

In one embodiment, the antenna consists of a slotted waveguide which hasslots on one of its lateral faces with a wave transmitter/receiverarranged at one end of the waveguide. The slots, also referred to asradiating slots, are inclined by a predetermined angle, preferablyalternately in one direction and in the opposite direction so that theradiated waves are in phase. The inclination of the aforesaid radiatingslots can vary over the length of the antenna, either from one radiatingslot to the other, or in groups of radiating slots.

Over the whole length of a waveguide antenna, substantially identicalreflectors are placed and extend virtually symmetrically with respect tothe plane of symmetry of the waveguide while making a predeterminedangle with one another in such a way as to reduce the depth of theradiation lobe of the antenna.

It should be observed that the sensing device according to the presentinvention has the advantage of discriminating between the direction andsense of displacement of a sensed moving agent, and thus takes intoaccount the angular component of the displacement. This selectivebehavior of the sensor according to the invention has the effect ofcancelling out the sensing of traffic parallel to the approaches to anautomatic door, for example.

In order to make the device usable as a protection system when it isfixed to one or more moving parts of an automatic device, the subject ofthe invention is also directed to a process for the electronicprocessing of the electrical sensing signal produced by the receiverincorporated within the sensing device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 represent schematic views of an example embodiment of theUHF part of a person and/or object sensor.

FIG. 4 shows a sensing lobe of a sensor associated with an automaticsliding door.

FIGS. 5 and 6 illustrate two examples of sensing lobes transmitted by ahorn antenna.

FIGS. 7 and 8 represent the sensing lobes at the approaches to anautomatic door equipped with a horn-antenna sensor.

FIG. 9 shows in a plan view the progress of pedestrians in theapproaches to an automatic door.

FIG. 10 illustrates the sensing of a pedestrian in the environment of anautomatic door at a sidewalk verge.

FIGS. 11 and 12 represent schematically an automatic revolving doorequipped with a conventional UHF protection device.

FIGS. 13 and 14 represent schematically an automatic pivoting doorequipped with a conventional UHF protection device.

FIGS. 15 and 16 represent schematically a roller shutter door equippedwith a conventional UHF protection device.

FIGS. 17 to 19 are views, similar to FIGS. 1 to 3, of the UHF part of asensor, equipped with an antenna sized so as to develop a wide, shallowlobe, or a narrow, deep lobe.

FIGS. 20 and 21 represent sensing lobes developed by the antenna shownin FIGS. 17 to 19.

FIG. 22 is an illustration of the matrix lobe developed by an activeinfrared sensor in front of a sliding automatic door.

FIG. 23 shows an ultrasound-based multilobe sensing system.

FIG. 24 represents a slotted waveguide.

FIGS. 25 and 26 are schematic views of an embodiment of a slottedwaveguide antenna according to the invention.

FIG. 27 shows, on a relative scale, the distribution of power along aslotted waveguide antenna.

FIG. 28 depicts the polar radiation diagram of the slotted waveguideantenna illustrated in FIGS. 25 and 26.

FIGS. 29 and 30 represent, respectively in transverse section and inelevation, the slotted waveguide antenna represented in FIGS. 25 and 26,but furnished with reflectors.

FIG. 31 depicts the polar radiation diagram of the slotted waveguideantenna illustrated in FIGS. 29 and 30.

FIG. 32 illustrates a method of fixing reflectors on a waveguide.

FIG. 33 represents a slotted waveguide antenna with reflectors, thewhole formed from an extruded piece.

FIG. 34 illustrates an embodiment similar to that illustrated in FIG.33, but formed of two assembled parts.

FIG. 35 illustrates another embodiment of an antenna according to theinvention.

FIG. 36 shows a slotted waveguide antenna according to the inventionformed with an extruded casing.

FIG. 37 is a schematic representation of an automatic transport vehicleequipped with a sensor with antenna according to the invention.

FIG. 38 represents a sliding automatic door equipped with a sensoraccording to the invention.

FIG. 39 is a schematic view in transverse section of a revolving doorequipped with sensors according to the invention.

FIG. 40 shows the evolution of the signal delivered by a motion sensorwith antenna according to the invention fixed to the lower part of aroller shutter door in the case where no obstacle is present in thesensing field.

FIG. 41 is similar to FIG. 40, but represents the signal when analuminum plate is slipped into and then withdrawn from the sensingfield, at ground level.

FIG. 42 is similar to FIG. 40, but represents the signal when a hand isslipped into and then withdrawn from the sensing field, at around 1 mfrom the ground.

FIG. 43 shows the evolution of the signal delivered by a motion sensorwith antenna according to the present invention, fixed to the upper partof a leaf of a revolving door, in the case where no obstacle is presentin the sensing field, and in the case where a hand is introduced intoand then withdrawn from the sensing field.

FIG. 44 shows another embodiment of the sensing and protection device ofthe present invention in which the reflectors are arranged so as topivot about an axis parallel to the longitudinal axis of the waveguide.

DETAILED DESCRIPTION

As is conventionally known, a Doppler effect UHF motion sensor isconventionally composed of a UHF part proper, comprising atransmit/receive module and an antenna, as well as an electronic circuitensuring the supply to the sensor and the processing of the Dopplersignal. FIG. 1 is a schematic view of the UHF part of a sensor of theaforesaid type: the transmit/receive module 10 and a horn antenna 20 canbe seen. FIG. 2 is a similar view after rotating the assembly by 90°about its longitudinal axis. FIG. 3 represents a front view of theassembly.

The transmit/receive module, conventionally known, for example as shownin FIG. 2 includes a resonant cavity in which a correctly supplied Gunndiode 11 generates a UHF signal which is radiated into space by virtueof the antenna 20. The module works for example at a frequency of 24.125GHz (K band). It goes without saying however that the description whichfollows is valid for other frequencies. Only the dimensions of thevarious constituent elements of this UHF part depend on the frequency ofthe transmitter/receiver. The horn of the antenna 20 radiates in the twoplanes containing its axes of symmetry 21 and 22. Any obstacle inrelative motion in the field of action of the sensor reflects part ofthe incident wave and the wave thus reflected is detected by the antenna20 and mixed with the incident wave by virtue of a Schottky diode 12correctly stationed in that portion of the waveguide situated betweenthe resonant cavity comprising the Gunn diode 11 and the antenna 20.Consequently, and by reason of the Doppler effect, a low-frequencysignal is available at the terminals of the Schottky diode 12. Thefrequency of the Doppler signal is proportional to the relative speed ofthe sensed obstacle and its amplitude is proportional to the size andproximity of the sensed obstacle. In the absence of a target in motionin the sensing field of the sensor, the signal at the terminals of theSchottky diode 12 is a noise signal of virtually zero amplitude.

Returning to the example represented in FIG. 1, the Doppler signalavailable at the terminals of the Schottky diode 12 is fed into anelectronic sensing circuit (not represented) capable of producing anactive signal for controlling the automatic unit which controls anautomatic device, for example an automatic door, when a person or objectin motion has been sensed in the sensing field.

Conventionally, the Doppler effect UHF motion sensor, intended in thisinstance to deliver a sensing signal to the automatic door for example,is stationed in the upper part of the latter and transmits the UHFsignal from top to bottom according to a determined angle.

The portion of space situated in front of the sensor and in which anyperson or object in motion can be sensed constitutes what is generallycalled the sensing lobe. FIG. 4 shows the sensing lobe of a sensor 30associated with a sliding automatic door 40. It takes the form of anoblique cone 50 whose base 60, hatched at ground level, is ellipsoidalin shape. The axis of this cone makes, together with the vertical, adetermined angle α. The shape and size of the sensing lobe are imposedby the dimensions of the antenna and by the sensitivity of theelectronic sensing circuit.

FIGS. 5 and 6 illustrate sensing lobes 60 transmitted by a horn antenna.The radiation characteristics of a horn antenna are such that, thecloser together are the opposite panels 70 and 71 of the antenna, thelarger is the width l of the corresponding lobe 60, and vice versa. Itis therefore seen that it is straightforward, on the basis of the sameantenna of rectangular cross section, to generate a narrow, deep sensinglobe 60 (as illustrated in FIG. 5) or, on the other hand, a wide,shallow sensing lobe 60 (as illustrated in FIG. 6). To do this itsuffices to perform a 90° rotation on the UHF part of the sensor, oreven on the sensor itself, so as to present the antenna with itsopposite panels 70 and 71 close together in order to develop a wide lobe60 (FIG. 6) or with its opposite panels 70 and 71 separated in order todevelop a narrow lobe 60 (FIG. 5).

In practice, it is convenient to represent the sensing lobe at theapproaches to an automatic door by a plan view corresponding to theintersection of the sensing lobe with the plane of the ground. The curvetraced is virtually ellipsoidal in shape, as represented in FIGS. 7 and8. Found therein by way of example are the plan view 40 of a slidingdoor, and the ground lobes 60 for two orientations of the antenna. FIGS.7 and 8 correspond to a UHF motion sensor working at a frequency of24.125 GHz, furnished with a horn antenna whose dimensions (see FIGS. 2and 3) are a=21 mm, b=7 mm and L=32 mm, this corresonding to an antennagain of around 10 dB. The sensor is stationed at a height of 2.20 mabove the ground. FIG. 7 corresponds to the case where the antenna ispresented with its opposite panels 70 and 71 far apart, thus enabling itto develop a narrow lobe, for example 2.20 m wide and 3 m deep. FIG. 8corresponds to the case where the antenna is presented with its oppositepanels 70 and 71 close together, thus enabling it to develop a widelobe, for example 3.40 m wide and 1.60 m deep.

The dimensional considerations relating to the sensing lobes developedby Doppler effect UHF motion sensors apply equally to UHF sensorscapable of sensing, in addition to the motion, the presence of personsor objects stationary in their sensing field. In this case, theprocessing of the signal is fundamentally different than the processingof the Doppler signal described above, but what was said regarding thelobes developed by horn antennas remains valid in this application case.

The sensing procedure entails any person or any object in motion beingsensed irrespective of their angle of approach relative to the sensor,as illustrated in FIG. 9, wherein is found a transverse sectional viewof a sliding automatic door 40 equipped with a sensor 30 developing asensing lobe 60. The pedestrian 1, approaching the door perpendicularly,is sensed equally as well as the pedestrian 2 walking parallel to thedoor, and as the pedestrian 3 approaching the door obliquely. For anautomatic door situated in front of a very clear space, this method ofsensing is very appropriate and leads to efficient opening of the door.

However, a number of application cases require the sensing lobedeveloped by the sensor to be relatively shallow. This is for examplethe case for Doppler effect UHF motion sensors intended for controllingan automatic door 40 placed along a sidewalk 80 or a shopping arcade.FIG. 10 shows how the incessant traffic of pedestrians such as 2,strolling along the sidewalk without intending to pass through the door,should not cause the opening of the latter, whereas pedestrians such as1 should be sensed. A solution to this problem consists in employing thesensor 30, developing a lobe 60 which is wide but of reduced depth andis generally contained within the space separating the door from thesidewalk proper. A better solution would consist in endowing the sensorwith an extra function making it insensitive to any motion parallel tothe plane of the door, but this would increase costs.

This is also the case for UHF sensors intended to ensure the protectionof persons in front of the moving leaves of a revolving door, asillustrated in FIGS. 11 and 12. The sensor 30 is fixed to the upper partof a leaf 40 and it directs its sensing lobe 60 from top to bottom. Thesensing procedure should bring about the slowing down of, or evenstopping, the revolving door when a person moves into the latter at aspeed below the tangential speed of the leaf, and when they are at thepoint of being caught up with and hit by the leaf preceding them, withconsequences which may be damaging. Since the sensor, fixed to eachleaf, accompanies the latter in its rotational motion, it is desirablefor the depth of the sensing lobe, measured at ground level, to berelatively reduced. This makes it possible on the one hand to sensepersons advancing at normal pace into the sectors of the revolving door,and on the other hand not to sense insignificant obstacles. Thus, as canbe seen in FIG. 12, a sensor developing a deeper sensing lobe, such as61, would bring about the undesired sensing of the fixed edges denoted90, 91 of the outer envelope of the revolving door.

A case very similar to the previous one is that of UHF sensors intendedto ensure the protection of persons in front of or behind the movingleaf of a pivoting door, as illustrated in FIGS. 13 and 14. The sensor30 is fixed to the upper part of the leaf 40 and it directs its sensinglobe 60 from top to bottom. The sensing procedure should bring about theslowing down of, or even the stopping, the pivoting door when a personis moving nearby while the former is in motion and liable to hit theperson with damaging consequences. Since the sensor, fixed to the movingleaf, accompanies the latter in its rotational motion, it is desirablefor the depth of the sensing lobe, measured at ground level, to berelatively reduced so as not to sense insignificant obstacles. Thus, asillustrated in FIG. 14, the sensor 30 developing a deeper sensing lobe,such as 61, would bring about the undesired sensing of a wall 100 whilethe door is still in the opening phase, or, for a sensor 31 situated onthe other side of the door, and also developing a deeper lobe, such as61, the undesired sensing of a fixed upright of the door such as 101.

Another case still requiring the use of a sensor having a shallowsensing lobe relates to the protection of the horizontal lower edge of aroller shutter door. A roller shutter door or sectional door takes theform of a shutter, consisting of sections hinged to one another, movingvertically by translating in lateral guides, and winding up, in itsupper part in the manner of a shutter, as illustrated in FIG. 15. Thedangerous part of this kind of door is the lower edge thereof. Duringthe drop motion of the door, its lower edge can hit and possibly injurea person standing underneath. Similarly, an object abandoned within theradius of action of the door may be damaged by the latter. Protection ofthis danger zone can be effected by a sensor 30 fixed under the edge ofthe roller shutter door 40 and directing its sensing lobe 60 from top tobottom. The sensing procedure should bring about the slowing down of, oreven stopping, the roller shutter door in the event of danger. Since thesensor, fixed to the moving door, accompanies the latter in itstranslational motion, it is desirable for the depth of the sensing lobe,measured at ground level, to be relatively reduced so as not to senseinsignificant obstacles. Thus, as illustrated in FIGS. 15 and 16, thesensor 30 developing a deeper sensing lobe, such as 61, would bringabout, for example, the undesired sensing of objects or vehicles presentnear the door, without there being a risk of them being hit, causing anuntimely and unjustified stopping of the door.

The list of the examples of the use of sensors having a narrow sensinglobe is obviously not limiting and is not restricted to the sphere ofautomatic doors. Any similar application should be considered as formingpart of the context of the invention which will be disclosed further on.

The technology of horn antennas allows partial resolution of the problemof sensing within a shallow lobe. Indeed, the dimensions of the sensinglobe depend strongly on the ratio of the dimensions of the rectangularcross section of the horn antenna. Furthermore, the further apart arethe opposite panels, the narrower is the corresponding lobe, and viceversa. The antenna 20 represented in FIGS. 17 to 19, and whosedimensions are, for example, a=50 mm, b=9 mm and L=36 mm makes itpossible, depending on its orientation, to develop a wide, shallow or anarrow, deep lobe. In this case also, the transmitter/receiver module 10works, for example, at a frequency of 24.125 GHz. The gain of theantenna is of the order of 13 dB.

FIGS. 20 and 21 show conventional sensing lobes in the approaches to anautomatic sliding door such as they are projected by a horn antenna. Thesensor is stationed at a height of 2.20 m above the ground. FIG. 20corresponds to the case where the antenna is presented with its oppositepanels 70 and 71 far apart, thus enabling it to develop a narrow lobe, 1m wide for example, and 3 m deep for example. FIG. 21 corresponds to thecase where the antenna is presented with its opposite panels 70 and 71close together, thus enabling it to develop a wide lobe, 3.4 m wide forexample and 1 m deep.

It is, however, noted that, in the second case, the lobe is scarcelyshallower than 1 m. This makes the solution valid, within certainlimits, for the solving of the case of sensing along a sidewalk or ashopping arcade, requiring preferably a very shallow sensing lobe. Bycontrast, this solution would not apply satisfactorily to the examplesillustrated by FIGS. 11 to 16. A lobe 1 m deep would certainly bringabout untimely sensings. On the other hand, it does not enable thedirection and sense of displacement of sensed moving agents to bediscriminated. As a result this practical limitation of the technologyof horn antennas to lobes having dimensions not less than 1 m deep makesthe use of conventional UHF sensors inappropriate in many cases.

As was stated earlier, the foregoing is also valid for UHF presencesensors furnished with horn antennas.

It is certainly currently possible to control, to a certain extent,narrow-lobe sensing with other technologies. The technology of activeinfrared sensing, for example, proceeds through transmission of infraredradiations in a sensing lobe and through measurement of the scatteredradiation reflected by the environment or by any obstacle to be sensed.Sensors based on this technology sometimes have the advantage of sensingthe presence of stationary persons or objects. Furnished with correctlydimensioned cylindrical Fresnel lenses, this kind of sensor makes itpossible to sense the presence and motion of a person or object in asensing lobe which is generally wide but of very reduced depth, forexample less than 30 cm, and which constitutes a sensing or protectioncurtain.

Referring to FIGS. 10 to 14, it is apparent that the characteristics ofthe infrared curtain are perfectly suited to this kind of application.By contrast, the same is not true for the roller shutter doorillustrated in FIGS. 15 and 16, given that the useful range of activeinfrared sensors is often limited to 2.50 m, whereas roller shutterdoors are generally greater than 3 m in height, often reaching 5 m.

On the other hand, it is well known that active infrared optoelectronicsensors have a number of flaws inherent in their technology. There is,in particular, some sensitivity to the nature, color and reflectivepower of the background which they cover, that is to say to thecontrasts of the environment which, if it is fluctuating, may bringabout a fair number of spurious sensings. Only appropriate signalprocessing enables these sensors to escape from these flaws, but this isat the cost of some complexity.

Finally, it should be pointed out that a known alternative to thetechnique of active infrared sensing makes it possible to endow thesensor with a function of taking into account the angle of approach ofthe agent moving in the sensing field. This constitutes an advantage inthe situation illustrated in FIG. 10, where the pedestrians walkingalong the sidewalk (hence parallel to the plane of the door) withoutintending to enter, should not be sensed. This technique consists intransmitting infrared radiations in a matrix array of discretetransmitters, for example three rows of four columns, denoted L1, L2, L3and C1 to C4 in FIG. 22. The sensor 30 is then stationed, for example,in front of a sliding automatic door 40. The transmitters aresuccessively activated by horizontal scanning, L1-C1, L1-C2, . . . ,L3-C4, whilst the radiations are reflected by the environment into amatrix array of discrete receivers synchronized with the correspondingtransmitters. Signal processing, allied with image processing, makes itpossible to extract information about the direction and sense ofdisplacement of the sensed moving agent, represented by the arrow inFIG. 22. This processing is, however, relatively complex and sensorsbased on this technique are expensive. Moreover, they are affected byflaws inherent in active infrared technology.

Finally, the technique of presence detection--and a lortiori motiondetection--through measurement of the propagation time of ultrasoundwaves could be suitable in some of the aforesaid application cases.Ultrasound-based sensors have, however, some drawbacks, especiallyundesirable sensings due to modification of the sensitivity of thesensor as a function of the climatic conditions (temperature, humidity),sensitivity to air currents, sensitivity to vibrations and to mechanicalnoise, absence of sensing for targets which are not orthogonal or arecovered in absorbent materials such as wool or cloth, these situationsbeing common in the environment of an automatic door. The sensing lobe60 at ground level of such a sensor is generally circular with a fairlyreduced diameter of the order of 50 cm, as illustrated in FIG. 23. Amultiple sensor 30 is then mounted above the automatic door 40 and itdirects its ultrasound beams 50 from top to bottom.

The small size of the lobe is favorable to the application casesillustrated in FIGS. 10 to 16 as regards the depth of the lobes, but itis not appropriate in respect of the width of the lobe, because thesensing lobe is circular. It is, therefore, necessary, in most cases, touse several sensors simultaneously, as illustrated in FIG. 23, so as toextend the lateral coverage. This quite obviously raises the price ofthe installation. Furthermore, the technique scarcely lends itself tothe inclusion of the angular component of the motion of the sensedmoving agent.

Finally, in applications in which the sensor moves with the door or amoving element, the vibrations engendered by this motion cannot butrender the sensing unreliable.

The present invention affords a solution to the problem of sensingwithin a lobe of reduced depth, and it proposes a sensing device usingan antenna which ensures, in particular, sensing in a favored direction.

The concept on which the invention is based consists in utilizing thetechnology of UHF frequencies and in profiting from the properties of anelongate radiating antenna having several radiating slots distributedover the length of the antenna and placed in such a way that each ofthem radiates in a plane which is virtually perpendicular to thelongitudinal direction of the antenna.

An example embodiment of an elongate radiating antenna consists of awaveguide antenna with radiating slots, as illustrated for example inFIG. 24. This antenna consists of a rectangular waveguide 110. Thedimensions a and b of the latter depend on the frequency of thetransmitted wave; and one of the faces 111, generally narrower, isdrilled with equidistant slots 120 through which the electromagneticenergy is radiated. The wave transmitted in the guide and radiatedthrough the slots 120 is generated at one of the ends of the waveguideby an appropriate transmitter (not represented in FIG. 24). The slots120 are regularly spaced apart a distance equal to λg/2, where λg is thewavelength of the wave transmitted in the waveguide. Moreover, the slotsare inclined alternately by an angle θ in one direction and in theopposite direction, so that all the slots radiate in phase.

The presence of inclined slots 120 in the small side of the guide 111interrupts the surface currents 130 arising in the panels of the guidesubsequent to the propagation of the wave in the guide. This generates atransverse electromagnetic field whose propagation takes place in afavored direction 140 perpendicular to the small side of the waveguide.For an antenna emitting electromagnetic radiation at a frequency of24.125 GHz, the standard dimensions of the guide are a=10.668 mm andb=4.318 mm. At the chosen frequency, the wavelength in the guide is15.303 mm, this corresponding to a separation between the slots of 7.65mm. The slots have for example a width l=1 mm, their depth p is 1.50 mm,whilst they are inclined by an angle of θ=5° relative to the vertical.

In an example embodiment of the invention, illustrated in FIGS. 25 and26, one end of the waveguide is supplied by a transmitter/receiver 10,situated a distance equal to λg from the first slot and whose operatingprinciple was described earlier and illustrated in FIGS. 1 to 3. Theother end terminates at a matched load 150, consisting, for example, ofan absorbent situated 3/4 (λg) from the last slot. The matching of theterminal load makes it possible to ensure the most uniform possibledistribution of radiated power along the guide. Other embodiments of thematched terminal load are possible. The same is true for any variantaccording to which the radiating slots are cut from the large side ofthe waveguide.

The slotted waveguide antenna has a length dependent on the frequencyemitted and on the number of slots cut in the small side 111 of theguide. By way of example, an antenna working at 24.125 GHz andcontaining ninety slots has a length L=707.6 mm (see FIGS. 25 and 26).However, greater lengths, on the order of several meters, are perfectlypossible to construct.

FIG. 27 represents, on a relative scale, the distribution of power Palong a 1.50 m long antenna, with the number N of slots, for exampleninety, represented as abscissa. It is noted that the matched load makesit possible to obtain a lobe of very good longitudinal uniformity. As aresult, a first condition allowing the application of slotted guideantennas to sensors developing wide, shallow sensing lobes is achieved.Indeed, it is apparent from the applications illustrated in FIGS. 11 to16, that the lobe developed by the sensor should be as uniform aspossible in the width direction, that is to say parallel to the plane ofthe automatic door.

In the case of a slotted waveguide antenna of great length (e.g. >1 m),it is perfectly possible to optimize the distribution of power radiatedalong the waveguide by increasing the inclination θ of the slots as afunction of their distancing from the transmitter/receiver 10. Thismodification of the inclination θ of the slots can of course be done ingroups of slots: thus, the first n₁ slots may for example have aninclination θ₁, the next n₂ slots have an inclination θ₂, with θ₂ >θ1,and so on, so as to make the power uniform along the antenna.

The second condition to be achieved by the slotted waveguide antenna isto develop a lobe of very narrow angular aperture, in a planeperpendicular to the axis of the guide.

FIG. 28 shows the polar radiation diagram of the antenna illustrated inFIGS. 25 and 26. The slotted waveguide antenna is assumed perpendicularto the plane of the diagram, at the origin of coordinates, with slotsradiating downwards. It is observed, according to measurements made thatthe antenna radiates in a quasi isotropic manner, thus making theproduction of a narrow lobe impossible. Indeed, the conventional -3 dBaperture of the measured radiation lobe is 2×30°. Under these conditionsand depending on the sensitivity of the sensor, the theoretical depth ofthe sensing lobe for a sensing height of 2 m could attain a value of 2m.

In order to reduce the aperture angle of the radiated lobe in a planeperpendicular to the waveguide, the present invention provides for theuse of correctly dimensioned reflectors. These reflectors take, forexample, the form of metal plates 160 and 161, secured to the largesides of the waveguide, as illustrated in FIGS. 29 and 30, and make anangle α with one another encompassing the small side 111 of the slottedwaveguide. The metal reflectors 160 and 161 can be fabricated fromcopper or brass plates folded so as to make an angle α with one another,and can be welded to the large sides of the waveguide 110.

FIG. 30 represents a side view of the slotted waveguide antennarepresented in FIGS. 25 and 26, but furnished with the aforesaidreflectors 160, 161. The latter have an aperture angle α of 53.4° forexample and their width C is 30 mm. By virtue of these reflectors, whichvirtually play the role of the opposite panels 70, 71 of the hornantenna illustrated in FIGS. 5 and 6, the angular aperture of the lobe,in a plane perpendicular to the axis of the guide, is greatly reduced asshown by the polar radiation diagram of FIG. 31. It is observed therethat the conventional -3 dB aperture of the measured radiation lobe isreduced to 2×10°. Under these conditions, and depending on thesensitivity of the sensor, the theoretical depth of the sensing lobe fora sensing height of 2 m is less than 0.50 m, this clearly correspondingto the desired objectives for the applications illustrated in FIGS. 11to 16.

Another embodiment and related method of fixing the reflectors accordingto the present invention consists in fixing the metal plates on eitherside of the waveguide by virtue of the clipping system illustrated inFIG. 32. A U-member, denoted 170, clamps the two parts of the reflectors160 and 161 against the large sides of the waveguide 110. Fixing isperformed, for example, by press screws 180, regularly distributed alongthe waveguide. So as to ensure proper electrical continuity between thewaveguide 110 and each of the reflectors 160 and 161, a conductiveself-adhesive, such as, 190 can be used, as can any other conventionalmeans such as conductive adhesive or paste.

In another embodiment illustrated in FIG. 33, the waveguide 110 and thereflectors 160 and 161 are formed as a single piece of extruded aluminumfor example. The slots 120 (not visible in the drawing) are constructed,for example, by cutting out with the aid of special tooling, or bymachining.

Given the small dimensions of the slotted waveguide antenna withreflectors, it may be of interest, in order to accord betteraccessibility to the tooling for cutting out the slots, to make thisextruded aluminum member in two parts denoted 200 and 210 in FIG. 34.Part 200 corresponds to the waveguide 110 proper, whilst part 210corresponds to the reflectors 160, 161. Being semi-open, the member 210lends itself more readily to the cutting out of the slots 120, which arenot represented in the figure. The two parts 200 and 210 of thisembodiment are fixed to one another, for example by means ofself-tapping screws 220 placed regularly along the waveguide and screwedinto fixing flanges 230. Electrical continuity can be ensured by theaforesaid means 190, such as conductive self-adhesive tape, orconductive adhesive or paste.

In FIG. 34, the fixing flanges 230 have been represented at the level ofthe plane containing the slots 120. These flanges 230 can be situated atany level along the large sides of the waveguide 110. Other methods offixing the two parts 200 and 210 of the extruded slotted waveguideantenna (for example welding, adhesive bonding, crimping, grooving andthe like) are to be regarded as forming part of the invention.

A particularly interesting embodiment of the slotted waveguide antennafurnished with reflectors consists, according to the invention, inmaking this device in two parts arranged as described below and withreference to FIG. 35. The first part, denoted 250, consists of asemi-open extruded aluminum member, the bottom 110 of which plays therole of a waveguide part and the sides 160 and 161 of which play therole of reflectors. It is observed that two grooves 251 and 252 facingone another are cut along the whole of the internal part of the member.

The second part, denoted 260, consists of a metal strip inserted intothe two grooves 251 and 252. This strip plays the role of the radiatingface 111 of the waveguide thus closed, on the condition that the slots(not drawn) are provided, as was stated earlier. This solution has theadvantage of simplifying the machining of the slots in the strip 260,insofar as this operation can be performed before insertion thereof intothe member, thus ensuring the tooling for cutting the slots optimumaccessibility. It is clear that, in this embodiment, the slots will havea length substantially less than the width l of the strip. It has beendemonstrated that this did not in any way affect the characteristics ofthe radiated field.

The strip 260 can be fabricated from a metal flat of extruded copper oraluminum, for example. A particularly advantageous solution consists inusing an epoxy substrate covered with a copper metallization, such asused commonly in the manufacture of printed circuits. In this case, theradiating slots can be produced by photo-engraving, a process which isparticularly easy to implement, and which leads to an accurate andinexpensive solution.

In the case in which the angle of inclination θ of the slots is to beprovided in groups of slots so as to make the radiating power uniformwithin an antenna of great length, this variation can be effected bythreading, into the grooves 251 and 252, successive strips bearing slotshaving a different angle θ.

Finally, profit may advantageously be drawn from the use of extrudedaluminum members in order to make, in a single piece, according to theinvention, the casing of the sensor, the main part of the waveguide andthe reflectors: this is illustrated in FIG. 36. The casing of the sensorusing the slotted waveguide antenna is labelled 270, the main part ofthe waveguide is denoted 110 and the reflectors are denoted 160 and 161.As explained earlier, the radiating face of the waveguide consists of astrip 260 inserted into the grooves 251, 252, the said face beingdrilled with slots, which are not represented in the drawing. Theattraction of this placement is that the casing 270 thus constituted cancontain other facilities necessary for the operation of the sensor, suchas for example a printed circuit 280, inserted into the longitudinalgrooves 281 and 282.

To summarize, in one embodiment of the invention, the UHF presence ormotion sensor is equipped with a slotted waveguide antenna, which iscorrectly dimensioned and furnished with an appropriate terminal load soas to render the radiated power as constant as possible parallel to theaxis of the guide, and which is endowed with reflectors placed in such away as to limit the angular aperture of the radiated lobe. Theseplacements make it possible to produce a desired radiation lobe whosewidth is defined by the context of the application, but whose depth isto be reduced to 0.50 m or less.

Referring now to FIG. 44, still another embodiment of the sensing andprotection device of the present invention is shown in which thereflectors (160, 161) are arranged so as to pivot about an axis parallelto the longitudinal axis of the waveguide (110). Axis (290) and axis(291) are parallel to the longitudinal axis of the waveguide (110).Reflector (160) pivots with respect to axis (290). Reflector (161)pivots with respect to axis (291). The pivoting of one structure withrespect to another can be accomplished by any of a multitude of wayswhich are well known.

FIG. 37 illustrates the case of an automatic transport vehicle 240, forexample a wire-guided cart. The vehicle is equipped with a sensor 30furnished with a slotted waveguide antenna such as described earlier. Byvirtue of the device according to the invention, on the one hand, thewidth of the sensing lobe 60 can be matched to the width of the vehicleand is proportional to the length of the waveguide employed and, on theother hand, the depth of the lobe projected in front of the vehicle issufficiently reduced, by virtue of the reflectors used, to avoidpremature sensings, especially when the vehicle changes direction.

It should be observed that with an antenna according to the invention,the main direction of radiation indicated by the arrow 140 in FIG. 24,is perpendicular to the small side of the waveguide, and henceperpendicular to the sensor itself. However, transverse components alsoexist, but they are of far lower amplitude than the amplitude of thecomponent 140 of the electromagnetic field. Thus, the invention makes itpossible to produce a UHF motion sensor having a favored sensingdirection.

FIG. 38 represents a sensor 30 according to the invention placed on asliding automatic door 40. This sensor develops a sensing lobe denoted60 at ground level. As a result of the foregoing, it will thus bepossible to sense only moving agents possessed of a component ofvelocity perpendicular to the sensor, that is to say along thedirections denoted 140. The pedestrian 1, who is approaching the doorvirtually perpendicularly thereto, will be sensed whilst the pedestrian2, who is moving parallel to the door will not. Nevertheless, if duringhis movement, the pedestrian 2 bends his course towards the door, hegenerates a component of velocity towards the sensor and he will besensed. This selective behavior of the sensor according to the inventionis highly desirable when the sensor is installed for example on a doorclose to a sidewalk or a shopping arcade. In this case, the sensing ofparallel traffic constitutes a nuisance, insofar as the pedestrians whoare strolling parallel to the door do not generally intend to entertherethrough.

Naturally, the invention applies also to embodiments of antennasoperationally equivalent to those illustrated by FIGS. 25 and 26. Thisis especially the case for an antenna in which a field-effect transistor(FET) oscillator driven by a dielectric resonator (DRO) is used insteadof the transmitter/receiver 10 described earlier. This is also the casefor plane microstrip antennas having a number of interconnectedradiating elements, whose dimensions and separations allow the radiationof lobes similar to those which are radiated by the slotted waveguideantenna described above.

An advantageous alternative to this system for sensing parallel traffic,according to the present invention, consists in using a unidirectionaltransmitter/receiver, known per se, instead of the transmitter/receiver10 illustrated in FIGS. 25 and 26. This unidirectionaltransmitter/receiver consists for example of a resonant cavity, of aGunn diode for generating the electromagnetic wave, and of two Schottkydiodes which are out of phase by a fraction of the wavelength andconstitute two measurement channels. The two signals delivered by thetwo Schottky diodes are analyzed by a discriminator circuit which, as afunction of the phase shift of the signals, makes it possible todistinguish a moving agent which is approaching from a moving agentwhich is receding. The use of sensors which are sensitive solely tomotions of approach is thus possible.

The advantage of this alternative is twofold. Firstly, since slightfluctuations of velocity about the favored direction of sensing arepossible, a system with two out-of-phase channels will be moreinsensitive to these fluctuations for displacements parallel to the axisof the guide and the absence of sensing of parallel traffic will merelyperform better. Secondly, such a sensor does not sense moving agentswhich are receding. In the case of the application to an automatic door,this allows early closure of the latter, this being directed towardsenergy savings. Indeed, it is not necessary to keep the door open whilea person is receding therefrom.

Rather than using a two-channel transmitter/receiver to produce thealternative described above, it is possible also, according to theinvention, to use a single-channel transmitter/receiver as illustratedin FIGS. 25 and 26, and to make the second measurement channel from apassive cavity fixed instead of the terminal load and supporting aSchottky diode. This passive cavity has, for example, dimensions of thecavity 10 illustrated in FIGS. 1 to 3 but does not include a Gunn diode.Another way to produce this alternative according to the invention is touse the slotted waveguide antenna such as illustrated in FIGS. 25 and26, and to implant the second Schottky diode into the waveguide itself,between the last slot and the terminal load.

It should be pointed out that the sensing device according to theinvention can be used in a doubly advantageous manner on the movingleaves 40 of a revolving door, as illustrated in FIG. 39. On the onehand, the depth P of the lobe 60 is reduced by virtue of the invention.On the other hand, the sensor 30 is insensitive to the lateral traffic,that is to say parallel to the plane of the leaf 40. This is favorableinsofar as a pedestrian 250, at the moment he steps into an open sectorof the door, is possessed of a speed of displacement whose maincomponent 251 is parallel to the plane of the door. Now, it isabsolutely desirable to avoid a sensing in this initial phase of theprogress of the pedestrian.

In the applications illustrated in FIGS. 11 to 16, as in FIG. 39, thesensor is arranged on the moving part(s) of the automatic door, or onboard a vehicle. Whether it be a motion sensor or a presence sensor, aUHF sensor travelling with a moving object sees its environment changerelative to itself while it is travelling. It is entirely as if thesensor were fixed and the environment were in relative motion. Underthese conditions, the useful signal delivered by the sensor, either theDoppler signal or a signal proportional to the power reflected, variescontinuously as a function of the environment. Consequently, it isimpossible to fix a sensing threshold representative of an obstacle.

In order to make the use of a motion or presence sensor fixed on amoving device reliable, it is proposed, according to one aspect of theinvention, to utilize the sensing signals delivered in the mannerdescribed below.

A first example application of the process according to the inventionrelates to protection in the environment of the roller shutter doorillustrated in FIGS. 15 and 16. The dangerous motion with this kind ofdoor is the drop, which involves a risk of colliding with a person orobject. The lower edge of the shutter door 40 is equipped with a Dopplereffect motion sensor 30, furnished with an antenna according to theinvention having a sufficient length to ensure good coverage in width.If the evolution of the signal delivered by this sensor is recordedduring the motion of the door, between the top (open) position and thebottom (closed) position and in the absence of any obstacle in thesensing field, a sensing signal is obtained as represented in FIG. 40.It is noted that this signal is of increasing amplitude A(V) andcorresponds to the relative approach of the environment with respect tothe sensor, first distant (left part of the curve) and then closer andcloser (right part of the curve). The abscissae are graduated in time(from 0 to 30 seconds). Since the speed of displacement of the rollershutter door is constant, a second scale, proportional to the height ofthe lower edge of the door with respect to the ground, is also indicated(from 4 m to 0 m).

It is reasonable to imagine a priori that such a type of sensor, mountedon a door in motion and subjected to incessant vibrations, would producecurves of the evolution of the sensing signal which differ from oneclosure cycle to another. Tests performed under the conditions describedearlier have shown on the contrary that the measured curve depicted inFIG. 40 is perfectly repetitive from one closure cycle to another andcan, according to the invention, serve as reference for the sensinglogic procedure. In other words, the curve depicted in FIG. 40 is thesignature of the environment with respect to the sensor and canconstitute a reference curve which is used in the process according tothe invention.

This process consists in continuously measuring the useful signaldelivered by the sensor, for example a Doppler effect UHF sensor with aslotted waveguide antenna, and in comparing the measured value, at agiven instant, with the corresponding value of the reference curvestored previously. Any distortion with respect to the reference curveindicates the presence of an obstacle, it being possible to utilize thisinformation to ensure safety in the environment of the door. It istherefore useful, according to the invention, for the system forprocessing the signal delivered by the sensor to perform a cycle forlearning its environment beforehand. For this reason, it is convenientto architecture the signal processing and decision taking system arounda microprocessor.

During a learning cycle, the microprocessor, in the case of the rollershutter door illustrated in FIGS. 15 and 16, undertakes the acquisitionand storage of the useful signal as a function of time, that is to sayas a function of the position of the door and in the absence of anyobstacle in its environment. The stored signal has, for example, theshape of the signal illustrated in FIG. 40. If the drop speed of thedoor is not sufficiently constant, a position detector, known per se,can be used to clock the acquisition of the measurements. If need be,the gain of the signal amplifying chain can be made to vary as afunction of the position of the sensor with respect to the environmentso as to render the reference curve virtually constant.

Throughout any subsequent motion of the door, the microprocessorcompares the value measured at a given instant--hence for a determinedposition of the door--with the corresponding value of the referencecurve. If a distortion is apparent between these two values, thisimplies that the sensor has detected the presence of an obstacle, andthe decision procedure gives rise for example to the arresting of thedoor, or its raising.

This kind of distortion is clearly apparent in the following figures.FIG. 41 shows how an aluminum plate, introduced into and then withdrawnfrom the sensing field of the sensor protecting the roller shutter doordescribed earlier, affects the measured curve. It is seen that thealuminum plate is already sensed while the door is at a height of around3.50 m above the ground. This is due to the high reflectivity of theplate. FIG. 42 shows how this same sensor senses a hand introduced andwithdrawn from the sensing field at a height of one meter above theground. It is apparent that the hand is sensed while the door is at aheight of around 1.50 m above the ground.

A second example application of the process according to the inventionrelates to protection in front of the leaves of a revolving door, suchas represented in FIGS. 11 and 12. During a complete rotation of thedoor, the microprocessor undertakes the acquisition and storage of theuseful signal as a function of time, that is to say as a function of theangular position of the door and in the absence of any obstacle in itsenvironment. The stored signal has, for example, the shape of the signalA illustrated in FIG. 43. If the speed of rotation of the door is notsufficiently constant, a position detector, known per se, can be used toclock the acquisition of the measurements. For a proper understanding ofFIG. 43, it should be pointed out that, for reasons related to theacquisition system used, the ordinate axis is reversed, and has itsorigin at the level 5.

Throughout any subsequent motion of the door, the microprocessorcompares the value measured at a given instant--hence for a determinedangular position of the door--with the corresponding value of thereference curve. If a distortion is apparent between these two values,this implies that the sensor has detected the presence of an obstacle,and the decision procedure gives rise for example to the slowing down orarresting of the door. This kind of distortion is clearly apparent incurve B of FIG. 43, which corresponds to the presence of a handintroduced into and later withdrawn from the sensing field of thesensor.

The reference curve labeled A in FIG. 43 can, depending on the speed ofrotation of the door, be shifted proportionally towards positive ornegative ordinates. This is due to the passband of the signal amplifyingchain. Profit may advantageously be drawn from this characteristic whichdepends on the speed of rotation and which can be stored previously.Indeed, in the case of the revolving door which can operate with severalspeeds of rotation, the previous storing of the reference waves atseveral speeds makes it possible on the one hand to sense an obstaclewith greater accuracy, and on the other hand, to undertake an action onthe door as a function of the speed; more or less energetic brakingduring sensing.

The process according to the invention is not limited to the processingof the signal delivered by a Doppler effect UHF motion sensor furnishedwith an antenna according to the invention. It can advantageously beused within the framework of measurements made with other types ofsensors, such as for example active infrared sensors. In this case, themeasured, stored reference signal corresponds to the reflecting of theinfrared radiation by the environment, in the absence of any obstacle.

What is claimed is:
 1. An electronic device for sensing and protectionof a member selected from a group consisting of persons and objects in asensing lobe associated with an automatic device, said electronic devicefor sensing and protection comprising a wave transmitter covering adetermined spatial sensing field, and a wave receiver for controllingthe automatic device; a radiating antenna comprising a waveguidecomprising lateral faces, wherein one of the lateral faces includesslots arranged thereon, said slots effectuating radiation in planessubstantially perpendicular to a longitudinal direction of thewaveguide, wherein the wave transmitter and the wave receiver arearranged at one end of the waveguide; a matched load arranged at anopposite end of the wave guide; substantially identical reflectorsarranged over substantially the whole length of the waveguide, saidreflectors extending essentially symmetrically with respect tolongitudinal plane of symmetry of the waveguide and making apredetermined angle with one another, wherein the waveguide and thereflectors comprise at least one piece.
 2. The electronic device asclaimed in claim 1, wherein said one of the lateral faces includingslots thereon comprises a radiating face, said radiating face comprisinga separate piece of said at least one piece.
 3. The electronic device asclaimed in claim 2, wherein the reflectors are pivotable about an axisparallel to a longitudinal axis of the waveguide.
 4. The electronicdevice as claimed in claim 2, wherein said radiating face comprises amember selected from the group consisting of a metal strip and ametallized epoxy substrate.
 5. The electronic device is claimed in claim4, wherein said slots in said radiating face comprise a member selectedfrom the group consisting of drilled slots and photoengraved slots. 6.The electronic device as claimed in claim 5 wherein said radiating facecomprises a metal strip comprising drilled slots.
 7. The electronicdevice as claimed in claim 5, wherein said radiating face comprises ametallized epoxy substrate comprising photoengraved slots.
 8. Theelectronic device as claimed in claim 4, wherein the reflectors arepivotable about an axis parallel to the longitudinal axis of thewaveguide.
 9. The electronic device as claimed in claim 1, wherein saidat least one piece comprises a casing for a sensor, at least a part ofthe waveguide and the reflectors.
 10. The electronic device as claimedin claim 9, wherein the reflectors are pivotable about an axis parallelto a longitudinal axis of the waveguide.
 11. The electronic device asclaimed in claim 1, wherein the reflectors are pivotable about an axisparallel to a longitudinal axis of the waveguide.
 12. The electronicdevice as claimed in claim 1, wherein said slots are disposed ininclined planes at predetermined positions over a length of thewaveguide.
 13. The electronic device as claimed in claim 12, wherein theinclination of at least one of said inclined planes is different fromthe inclination of other inclined planes.
 14. The electronic device asclaimed in claim 13, wherein said inclinations vary over the length ofsaid waveguide.
 15. The electronic device as claimed in claim 13,wherein variation in the inclinations of the slots takes place per groupof a plurality of slots.
 16. The electronic device as claimed in claim1, wherein said at least one piece comprise two pieces.
 17. Theelectronic device as claimed in claim 1, wherein said at least one piececomprises an extruded piece.
 18. A process for sensing a member selectedfrom a group consisting of persons, animate objects and inanimateobjects in a sensing lobe associated with a movable automatic device bymeans of a sensor installed on the movable device so as to cover adetermined spatial sensing field and produce a sensing signal, saidprocess comprising the following steps:measuring said sensing signal asa function of motion of a movable automatic device in the absence of anyobstacle, storing an evolution of said sensing signal in an electronicmemory in order to serve as a reference curve, measuring a value of thesensing signal continuously as a measured value and comparing themeasured value with a corresponding value of said reference curve, usinga deviation between the measured value of said sensing signal and thecorresponding value of the reference curve to indicate a presence of anobstacle formed by a member selected from the group consisting ofpersons, animate objects and inanimate objects in the sensing field. 19.The process for sensing as claimed in claim 18, wherein the sensingsignal is captured and stored as a function of time.